^°l89o!"'] PROCEEDINGS OF THE NATIONAL MUSEUM. 211 



To the above enumeration and list must be added : 



(14) H. Ulizabethw Pilsbry, detected in the " Village of Amula, be- 

 tween Tixtla and Cliilopa, State of Guerrero, Southwestern Mexico," 

 a form which in its general features much resembles H. Gealei, and may 

 prove to be a geographical variety thereof. 



(15) H. semismdpta Stearns, near San Carlos, Chihuahua, Mexico. 



(16) H. arizonensis Stearns, Dos Cabezas, Arizona. 



Order CTENOBRANCHIATA. 



Suborder Streptodonta. 



Superfamily T.ENIOGLOSSA. 



Family Strepomatid^ Haldeman. 



Genus GONIOBA3IS Lea. 



Melaiiia (? Goniobasis) acutifilosa sp. nov. 



Plate XV, Fig. 9. 



Shell slender, elongated ; whorls rounded, convex ; sutures much 

 impressed. Spire eroded above the fourth whorl. Surface sculptured 

 with strong thread-like revolving keels alternating with broad channels; 

 of these keels there are usually six on the body whorl, sometimes 

 more, and generally three only on the preceding whorls, of which the 

 upper two are rather the most prominent and are usually interrupted 

 and regularly broken up, producing an evenly crenulated chain. Fol- 

 lowing the wind of the shell and just below the sutures, the whorls 

 broadly slope to the succeeding keel, which gives the shell a turrited 

 outline. Surface of shell a very dark horn color, blackish ; aperture 

 small, ovate, inside lighter colored than tlie surftice, the substance of 

 the shell being thin and partially translucent, the keels showing 

 through on the inside of the mouth, when held up to the light. Dimen- 

 sions of largest : Longitudinal, 10.50""" ; latitudinal, 7.50'""'. 



The foregoing description is based on an examination of some three 

 dozen specimens. 



Habitat. — Eagle Lake, California, where this well characterized 

 and interesting form was detected by Mr. Henry W. Henshaw, in 

 June, 1877. (U. S. National Museum collection, No. 60596.) 



The above species has the slender habit of other related West Ameri- 

 can forms, such as s//ic?^?ff Gould (= Shastaensis Lea), and nigrina, riibi- 

 ginosa, and Bairdiana, of Lea. Its sculpture relations are nearer to 

 oGcata Hinds, but that is a robust and more ventricose shell, closely 

 spirally sculptured over and throughout, and lacking the broad sub- 

 sutural slope and differing in other minor features as well as in the 

 character of the aperture, which in Hinds's species is much the largest 

 and more effuse. 



